According to an article by J. W. Vanderhoff et al., Journal of the Optical Society of America, vol. 44, pp 603 - 609 (1954), when monodispersed latices of polyvinyltoluene and polystyrene, wherein the particles have a diameter in the range from about 100 to about 1000 m.mu., are dried to form a frail film, the particles of the latex spontaneously arrange themselves in a close-packed crystalline arrangement.
The resulting film is characterized by an iridescent surface color. The crystalline samples show beautiful iridescent effects under the illumination of white light. Unfortunately, iridescent films produced in this manner are too fragile for practical use. If the films are heat treated their mechanical strength is considerably improved, but there is a marked decrease in diffracting power, since heat treated samples are more transparent then untreated samples. As the samples become clearer, the diffracting power becomes weaker and, after prolonged heat treatmement, the final film is transparent and non-diffracting. On the other hand, according to Japanese Patent Sho-45-32046, a method of producing the iridescent color has been proposed, wherein aqueous latices are dried or semi-dried to form iridescent films or lumps. Such iridescent materials are imbedded in polyester resins, PMMA and the like, in order to achieve the final stabilization of the iridescent material.
In this invention, however, no refractive index relationship between the materials used to imbed the iridescent material and latex particles has been considered. Therefore, iridescent effects produced are considered to be poor. Thus heretofore, there has been no way of providing a stabilized, three-dimensional close packed iridescent structure. The known iridescent films are too fragile for practical use in decoration or for ornamental use and, if such films are heat stabilized, they lose their pronounced iridescent characteristics. The other known iridescent materials, to which no refractive index relationship between particles and material used to imbed the iridescent films or lumps has been taken into account, are considered to have less iridescent effects.
We have succeeded in providing a stabilized, iridescent structure which has superior iridescent effects and has wide, practical utility for decorative and ornamental use.